250 



The Birches 



It is reported to grow to a height of about 26 meters, with a trunk 3 or 4 dm. thick, 

 but it is usually much smaller. It inhabits mountain sides and river banks. 

 The bark of the trimk is white or whitish, that of the branches pale reddish 



brown. When young the twigs are densely 

 resinous-glandular, becoming smooth and 

 red-brown. The buds are ovoid, blunt, 

 about 6 mm. long, their scales sometimes 

 fringed with white hairs. The leaves are 

 triangular-ovate, sharp-pointed, irregularly 

 sharply toothed, 4 to 8 cm. long, and usually 

 nearly as wide as long, firm in texture, 

 smooth when old, somewhat hairy when 

 young; they are dark green and dull on the 

 upper surface, hght green on the lower; the 

 slender leaf-stalks are 1.5 to 3 cm. long, the 

 stipules oblong. The staminate catkins are 

 borne 2 or more together, and have ovate 

 pointed scales. The ripe pistillate catkins 

 are cylindric, about 3 cm. long, i to 1.3 cm. 

 thick; their scales have hairy-fringed edges, 

 the lateral lobes wider but scarcely longer 

 than the pointed middle one ; the nut is oval, 

 about 2 mm. long, its wings rather broader than the body. 



It has been proposed to unite this species with the Betula pendiila Roth, of 

 northern Europe and Asia, but the foHage of the two seems abundantly distinct. 

 It has formerly been erroneously considered as identical with the Betula alba ver- 

 rucosa var. resinijera of northeastern Asia, and the name B. resinijera Britton 

 has been proposed for it. 



Fig. 205. Alaska Birch. 



4. PAPER BIRCH Betula papyrifera Marshall 



The Paper birch, or Canoe birch, grows mostly in forests, and ranges from 

 Newfoundland to Alaska, south to New Jersey, Pennsylvania, Michigan, Nebraska, 

 Colorado, and Washington, thus extending nearly or quite across the continent; 

 its leaf-form is somewhat variable, and it has been held by various authors as 

 identical with the White birch of Europe {Betula alba L.), but an examination of 

 the two trees growing side by side will at once demonstrate that, while similar, 

 they are different. It attains a maximum height of about 25 meters, with a trunk 

 diameter of about 7 dm. B. Andrewsii A. Nelson, is probably not distinct. 



The bark is usually bright white outside, orange oryellow within, quite thick, and 

 peels off readily in thin layers; at the bases of old trees it is often black and rather 

 deeply fissured, and there are often black bands higher up on the trunks. The 

 young green twigs are a little viscid and quite hairy; they become smooth and 



